1. Field of the Invention
The present invention relates generally to methods and apparatus used in harvesters to dislodge produce from upstanding plants, and more particularly to oscillating beaters used in the harvesters.
2. Background Art
There are harvesters, such as shown in U.S. Pat. No. 3,184,908 (Rust), [FIG. 2], which have harvesting units comprising a vertical hub mounted for free rotation about a vertical axis and a plurality of beater rods attached to the hub and extending radially outwardly therefrom. The harvester typically moves along a row of upstanding plants so that the beater rods engage the plants so as to strike or vibrate the plants, thereby dislodging the produce from the plant for collection. Because the hub is free wheeling, the rods, in effect, walk through the plant as the harvesting unit moves along the row. In the Rust device, the beater rods oscillate simply up and down.
With harvesting, an underlying problem is that harvesting desirably is done quickly and this involves vigorous shaking or acceleration of the beater rods. However, the acceleration which is used to shake the produce from the plants must not be excessive so as to injure the plants and the produce. Furthermore, in order to maximize the harvesting yield, an important consideration is being sure to reach all the portions of the plants which contain ripe produce, i.e., to cover the entire vertical length of the plant with the beaters.
As the Rust device illustrates, when the beater rods are oscillated in an up and down motion which is substantially harmonic motion the rods oscillate about an equilibrium position in an oscillation region (which extends from one amplitude above the equilibrium position to one amplitude below the equilibrium position). While this oscillation region may cover an entire vertical spacing distance, which is a vertical distance between the rods, thereby seeming to cover the entire vertical length of the plant, the action of the rods is uneven. In as much as the up and down motion approximates simple harmonic motion, which is characterized by maximum velocity of the rods as they cross the equilibrium position and minimum velocity of the rods at the outer edges of the oscillation region, the rods impart a relatively high velocity to branches which are contacted near the equilibrium position and a relatively low velocity to branches which are contacted by the rods near the edges of the oscillation region. This leads to uneven harvesting and uneven coverage of the plant.
Furthermore, in the case of the Rust device, so that in moving up and down the rods are able to traverse the entire vertical length of the plant, the oscillation of the beater rods must necessarily have a relatively large amplitude. In order to avoid giving the rods too high an acceleration which may damage the plants, with the acceleration of the rods being a function of both a frequency and the amplitude of the motion, the frequency must be reduced to compensate for the large amplitude. Accordingly, the amplitude imposes a limit on how high the frequency may be, and vice versa. Sometimes this results in slower harvesting.
In some settings, an external wire may be used. U.S. Pat. No. 3,371,473 (Burton) shows a horizontal tensioned wire 10, upon which are supported the plants to be harvested and which moves up and down with the plants. A shaking mechanism, which is a hub mounted for free rotation about a tilted axis x--x and which has a single tier of evenly spaced radially projecting arms, engages and shakes the wire 10 and the plants. The arms are shaken back and forth along another tilted axis y--y, so that as the mechanism moves along the wire, the arms walk through the plants and the hub rotates with the arms, thereby enabling the arms to engage the wire 10 from underneath. Each arm is made of a slightly longitudinally undulating shape which provides a longitudinally extending recess 25 along the center of the arm. The effectiveness of each arm depends upon the time that the arm is able to maintain operative contact with the underside of the wire 10. The undulating shape of the arm is directed at restraining the movement of the wire 10 and drawing the wire 10 toward the axis of the hub. (An outwardly and upwardly turned horn 28 at the end of the arm also helps to engage and draw the wire 10 toward the hub.)
In many harvesting applications such wires are not visible. This may be for a number of reasons including the labor costs of stringing and tying the wire. Thus, often the beater rods must shake the plants directly.
Rather than using an up and down motion, there are harvesters which impart an orbital motion of one kind or another to the beater rods. For example, U.S. Pat. No. 3,494,117 (Weygandt et al) shows a drum or a head 13 which, in all embodiments of the patent, is mounted for free rotation about a vertical axis and which has a plurality of vertically spaced and radially projecting tines 16 attached thereto. Within the head 13 are various arrangements of counterweights which swing in various ways on levers to impart a desired movement to the tines. In a first embodiment (FIGS. 2 and 3), the counterweights cause the head 13 to orbit about an axis which is transverse to the path of the harvesting machine, i.e., orbit about the transverse axis within a vertical plane. Consequently, the tines 16 that at any time are disposed transversely of the vehicle and that engage the plant, (the "active tines") orbit in a plane normal to the length of the active tines 16. The motion of the beater rod is circular, rather than up and down as in the earlier described prior art. The motion approximates uniform circular motion, which has a constant linear velocity. However, when a vertical component of the circular motion is considered, and in many settings this vertical component is the important component for purposes of shaking the branches, the vertical component again has its maximum velocity when it crosses a central location, i.e., the equilibrium position, and has its minimum velocity at the extreme upper and lower edges of its region of oscillation. In other words, while the rod is moving with constant linear velocity in a circle, a branch which contacts the rod at the extreme upper and lower edges of the circle may merely graze the rod, and a branch which contacts the rod near the central zone of the circle will be accelerated sharply at right angles to the length of the branch. The latter branch receives a much stronger shake than the former branch. Thus the orbital motion may in many settings provide an uneven shaking to the bush.
In a second embodiment (FIGS. 4 and 5), the counterweights act to cause a torsional oscillation of the head 13a, which is combined with a vertical up and down shaking, so as to cause all of the tines 16a on the head 13a to move in cylindrical paths about a stationary lengthwise axis of the tines 16a. The cylindrical paths of the second embodiment are like the cylindrical paths of the first embodiment. In other words, under certain conditions, the tines 16a will unevenly cover the plant. Again, the frequency and amplitude of the orbital motion may have to be carefully balanced in order to avoid injuring the plant. Again, to obtain the desired full vertical coverage of the plant, the amplitude of the orbit must be relatively large and therefore the frequency must be correspondingly reduced. In a third embodiment (FIGS. 6 and 7) the counterweights act to make the head 13b, which is again vertically disposed, to oscillate through a simple arc, back and forth about an axis 121 which is vertical and which is external to the head 13b. Thus, the tines 16b, in effect, wiggle horizontally as the head 13b rotates in a freely rotating fashion through the plants.
Another device which imparts an orbital motion is shown in U.S. Pat. No. 4,292,792 (Burton). The patent shows a vertical shaft 25 (FIG. 7) which supports a plurality of vertically spaced, radially projecting beater rods and which is mounted for free rotation on a smaller, concentric shaft 81. As the beater rods extend radially the beater rods are tilted. The assembly, including the rods, the shaft 25, and the shaft 81, moves atout another vertical shaft means 63 (a lower part of which is numbered 64), thereby moving, as is shown in the top view of FIG. 8, in a circular, horizontal orbit 68. Accordingly, the beater assembly orbits horizontally into and out of the plants, with the beater rods being held in the tilted orientation.
While the prior art harvesters approach the problem of covering the plants evenly, and offer various forms of orbital motion of the beater rods to do this, the prior art still has not found a satisfactory way to bring the entire plant into contact with the rods with the rods moving at a velocity which is neither too high or too low. Additionally, a means is needed to improve the contact between the beater rods and the branches so that the rods contact the branches at more locations.
A search of U.S. Patent literature, in addition to disclosing the four patents mentioned, shows the following patents:
U.S. Pat. No. 4,222,219 (Lasswell) shows a fruit picking machine with looped spindles that rotate about a horizontal axis projecting horizontally into the fruit tree.
U.S. Pat. No. 3,987,608 (Wilcox Jr.) shows in FIG. 2 downwardly concave horizontal fruit picking fingers for grasping fruit from trees.
U.S. Pat. No. 3,968,631 (Haines) shows curved fruit picking fingers which come into contact with the fruit.
U.S. Pat. No. 3,827,222 (Toti) shows picking arms which individually rotate about a horizontal axis, which include an offset nose portion which moves eccentrically relative to the axis of the arm.
U.S. Pat. No. 3,596,457 (Van Tine) shows a shaft, with spoked rods arranged in spaced tiers emanating from the shaft, rotating about a longitudinal axis and reciprocating back and forth on its support.